Выбор зондирующего сигнала для радиолокационного комплекса в режиме синтезированной апертуры антенны

В работе рассмотрены методы формирования зондирующего сигнала для радиолокационной станции в режиме синтезированной апертуры антенны, обеспечивающие минимальный уровень боковых лепестков в плоскости дальность-азимут. Показано, что наилучшим по указанным критериям является фазоманипулированный сигнал с минимально возможным уровнем боковых лепестков импульсной автокорреляционной функции.Работа выполнена при финансовой поддержке в рамках государственных контрактов № 02.G25.31.0204, №2.9140.2017/БЧ, №2.2226.2017/ПЧ и гранта РФФИ №15-07-99514а

Generalized discrete Fourier transform with non-linear phase : theory and design

Constant modulus transforms like discrete Fourier transform (DFT), Walsh transform, and Gold codes have been successfully used over several decades in various engineering applications, including discrete multi-tone (DMT), orthogonal frequency division multiplexing (OFDM) and code division multiple access (CDMA) communications systems. Among these popular transforms, DFT is a linear phase transform and widely used in multicarrier communications due to its performance and fast algorithms. In this thesis, a theoretical framework for Generalized DFT (GDFT) with nonlinear phase exploiting the phase space is developed. It is shown that GDFT offers sizable correlation improvements over DFT, Walsh, and Gold codes. Brute force search algorithm is employed to obtain orthogonal GDFT code sets with improved correlations. Design examples and simulation results on several channel types presented in the thesis show that the proposed GDFT codes, with better auto and cross-correlation properties than DFT, lead to better bit-error-rate performance in all multi-carrier and multi-user communications scenarios investigated. It is also highlighted how known constant modulus code families such as Walsh, Walsh-like and other codes are special solutions of the GDFT framework. In addition to theoretical framework, practical design methods with computationally efficient implementations of GDFT as enhancements to DFT are presented in the thesis. The main advantage of the proposed method is its ability to design a wide selection of constant modulus orthogonal code sets based on the desired performance metrics mimicking the engineering .specs of interest. Orthogonal Frequency Division Multiplexing (OFDM) is a leading candidate to be adopted for high speed 4G wireless communications standards due to its high spectral efficiency, strong resistance to multipath fading and ease of implementation with Fast Fourier Transform (FFT) algorithms. However, the main disadvantage of an OFDM based communications technique is of its high PAPR at the RF stage of a transmitter. PAPR dominates the power (battery) efficiency of the radio transceiver. Among the PAPR reduction methods proposed in the literature, Selected Mapping (SLM) method has been successfully used in OFDM communications. In this thesis, an SLM method employing GDFT with closed form phase functions rather than fixed DFT for PAPR reduction is introduced. The performance improvements of GDFT based SLM PAPR reduction for various OFDM communications scenarios including the WiMAX standard based system are evaluated by simulations. Moreover, an efficient implementation of GDFT based SLM method reducing computational cost of multiple transform operations is forwarded. Performance simulation results show that power efficiency of non-linear RF amplifier in an OFDM system employing proposed method significantly improved

Optimisation des formes d'ondes d'un radar d'aide à la conduite automobile, robustes vis-à-vis d'environnements électromagnétiques dégradés

Several driver assistance radars are developed for security and comfort requirements. Their goal is among others to detect the presence of obstacles for collision avoidance. The current demand in terms of automotive radar sensors experience a significant growth and the technologies being employed must ensure good performances especially in an environment degraded by interfering signals of other users. In this thesis, we are interested in developing a radar system which is effective in all situations especially in a multi-user context. For this purpose, we propose novel radar waveforms based on the combination of frequency hopping Costas codes and other pulse compression techniques, using modified Costas signals. The design approach allows to synthesize a significant number of waveforms, thanks to the high diversity introduced. Afterwards, we have exploited two estimation of target parameters approaches. The first one, quite classic, is based on Doppler processing in a coherent pulse train. The second one, recent in the automotive field , is based on the Compressed sensing techniques. An adaptation of these algorithms to proposed signals is discussed in noisy and multi-target environments. All these works contribute in one hand to explore novel radar waveforms, complement to those currently used in automotive radars and in another hand to propose an innovative processing at the receiver level, suited to radar applications in general and automotive ones in particular.Divers radars sont développés pour des besoins d’aide à la conduite automobile de sécurité mais aussi de confort. Ils ont pour but de détecter la présence d’obstacles routiers afin d’éviter d’éventuelles collisions. La demande actuelle en termes de capteurs radars pour l’automobile connaît une croissance importante et les technologies employées doivent garantir de bonnes performances dans un environnement dégradé par les signaux interférents des autres utilisateurs. Dans cette thèse, nous nous intéressons au développement d’un système radar performant en tout lieu et en particulier dans un contexte multi-utilisateurs. A ce propos, nous proposons de nouvelles formes d’ondes qui se basent sur la combinaison des codes fréquentiels de Costas et d’autres techniques de compression d’impulsion en exploitant les signaux de Costas modifiés. La conception adoptée permet, grâce à la diversité introduite, de synthétiser un nombre important de formes d’ondes. Nous avons, ensuite, exploité deux approches d’estimation des paramètres des cibles. La première, plutôt classique, se base sur le traitement Doppler dans un train d’impulsions cohérent. La deuxième, récente dans le domaine automobile, se base sur la technique dite de « Compressed Sensing ». Une adaptation de ces algorithmes pour les signaux proposés a été discutée dans des environnements bruités et multi-cibles. L’ensemble de ces travaux contribue à explorer de nouvelles formes d’ondes, autres que celles utilisées dans les radars actuels et à proposer un traitement innovant en réception, adapté aux radars en général et à l’automobile en particulier

Methodology of synthesis and signal processing of generalized binary Barker sequences for spread spectrum communications

Дисертація на здобуття наукового ступеня доктора технічних наук за спеціальністю 05.12.02 – «Телекомунікаційні системи та мережі». – Національний авіаційний університет, Київ, 2019. У дисертаційній роботі вирішується актуальна науково-технічна проблема синтезу бінарних дискретно-кодованих послідовностей (ДКП), які є оптимальними за мінімаксним критерієм щодо їх автокореляційної функції (АКФ), у частині синтезу регулярних структур цих ДКП та їх комбінаторних систем в умовах обмежень на максимальний рівень абсолютних значень бічних пелюсток їх АКФ (ДКП Баркера). Вирішенням зазначеної проблеми у дисертації є новий синтезований тип ДКП – узагальнені бінарні послідовності Баркера (УБПБ), які характеризуються регулярними структурами, можуть бути синтезовані регулярними методами синтезу та утворюють нові мультиплікативно комплементарні структури бінарних ДКП. У роботі розроблено методологію синтезу та обробки УБПБ та їх мультиплікативно комплементарних структур, яка у своєму складі містить розроблену параметрично-критеріальну модифікацію EM-алгоритму з видаленням компонент гаусівської змішаної моделі для аналізу кореляційних зв’язків у системах ДКП та доведені теореми про його математичну сингулярність за певних умов такого статистичного аналізу для обґрунтування введених у модифікації алгоритму критеріїв, розроблені метод структуризації ДКП з апріорі невідомими внутрішніми структурами, регулярний метод синтезу УБПБ, метод синтезу та сумісної обробки мультиплікативно комплементарних структур УБПБ, метод декомпозиції структури вихідного сигналу системи обробки мультиплікативно комплементарних УБПБ, метод39 оцінювання енергетичних параметрів ортогональних сигнально-кодових конструкцій та завад при передаванні УБПБ. У дослідженні також обґрунтовано класифікацію УБПБ, виявлено та досліджено системні властивості регулярних структур УБПБ та їх АКФ, синтезовано повну систему математичних моделей для аналітичного опису АКФ УБПБ, розроблено аналітичні моделі оцінювання показників якості передавання повідомлень у телекомунікаційних системах при використанні УБПБ.Диссертация на соискание учёной степени доктора технических наук по специальности 05.12.02 – «Телекоммуникационные системы и сети». – Национальный авиационный университет, Киев, 2019. Диссертационная работа посвящена решению актуальной научно-технической проблемы синтеза бинарных дискретно-кодированных последовательностей (ДКП), оптимальных по минимаксному критерию в отношении их автокорреляционной функции (АКФ), в части синтеза регулярных структур этих ДКП и их комбинаторных систем в условиях ограничений на максимальный уровень абсолютных значений боковых лепестков их АКФ (ДКП Баркера). Решением указанной проблемы в диссертации является новый синтезированный тип ДКП – обобщённые бинарные последовательности Баркера (ОБПБ), которые характеризуются регулярными структурами, могут быть синтезированы регулярными методами синтеза и образовывают новые мультипликативно комплементарные структуры бинарных ДКП. В работе разработана методология синтеза и обработки ОБПБ и их мультипликативно комплементарных структур, которая в своём составе содержит разработанную параметрически-критериальную модификацию EM-алгоритма с удалением компонент гауссовской смешанной модели для анализа корреляционных связей в системах ДКП и доказанные теоремы о его математической сингулярности в определённых условиях такого статистического анализа для обоснования введённых в модификации алгоритма критериев, разработанные метод структуризации ДКП с априори неизвестными внутренними структурами, регулярный метод синтеза ОБПБ, метод синтезу и совместной обработки мультипликативно комплементарных структур ОБПБ, метод декомпозиции структуры сигнала на выходе системы обработки мультипликативно комплементарных ОБПБ, метод оценивания энергетических параметров ортогональных сигнально-кодовых конструкций и помех при передаче ОБПБ. В исследовании также обоснована классификация ОБПБ, выявлены и исследованы системные свойства регулярных структур ОБПБ и их АКФ, синтезирована полная система математических моделей для аналитического описания АКФ ОБПБ, разработаны аналитические модели оценивания показателей качества передачи сообщений в телекоммуникационных системах при использовании ОБПБ.Thesis for a degree of Doctor of Technical Science in specialty 05.12.02 – «Telecommunication Systems and Networks». – National Aviation University. – Kyiv, 2019. The thesis is devoted to solving the actual scientific and engineering problem dealing with a synthesis of binary sequences, which are optimal by the minimax criterion with respect to their autocorrelation function, in terms of a synthesis of regular structures of these binary sequences and their combinatorial systems under additional restrictions on the peak sidelobe level of their autocorrelation function (Barker sequences). The solution of the problem, proposed in the thesis, boils down to a new synthesized kind of binary sequences – generalized binary Barker sequences, which are characterized by regular structures, can be synthesized by means of regular synthesis method and form new multiplicative complementary structures of binary sequences. The methodology of synthesis and signal processing of generalized binary Barker sequences and their multiplicative complementary structures, developed in the thesis, consists of: (a) the modification (parametric and criteria features) of the expectationmaximization (EM) algorithm with removing components of the Gaussian mixture model and additional clustering criteria for a statistical analysis of cross-correlations between sequences in a system for their further structuring, based on proved theorems on mathematical singularities in the log-likelihood function in the mentioned statistical analysis of cross-correlations; (b) the method of structuring binary sequences with a priori unknown structures, which provides selecting groups of binary sequences with interconnected structures and further detecting these interconnected structures in an explicit form; (c) the regular method for synthesis of generalized binary Barker sequences, based on the deterministic generation rules for these sequences; (d) the method for synthesis and joint signal processing of multiplicative complementary structures of generalized binary Barker sequences, based on the multiplication of results of matched filtering of signal components; (e) the method of a structural decomposition of output signal in signal processing system for multiplicative complementary generalized binary Barker sequences (an output signal can be represented by some number of separately taken partial lobes, each of which is characterized by constant mean value and variance of signal), which allows to perform a statistical analysis of output signal for noise immunity analysis, detection and other purposes in telecommunication system; (f) the method of estimation of energetic parameters of orthogonal signal-code constructions and noise on the physical layer of telecommunication system in case of use of generalized binary Barker sequences. The classification by types and subtypes of generalized binary Barker sequences, based on statistical clustering using the EM and k-means algorithms, is also justified in the research. The properties of regular structures of generalized binary Barker sequences and properties of their autocorrelation functions are detected and studied. A complete system of mathematical models for analytical description of the autocorrelation function of generalized binary Barker sequences is synthesized. The analytical models for estimation of quality characteristics on the physical layer of telecommunication system in case of use of generalized binary Barker sequences are developed. Spectral and detection features of generalized binary Barker sequences and their comparison with Golay complementary sequences are also studied in the research. In contrast with Golay complementary sequences, generalized binary Barker sequences provide larger values of the processing gain in sidelobes (by 4.1 dB for a considered case), which provides less noise in sidelobes and a lower number of errors of the first genus in the case of the use of generalized binary Barker sequences. At the same time, the main disadvantage of generalized binary Barker sequences in comparison with Golay complementary sequences is that the processing gain in the main central lobe is lower (by 8.9 dB for a considered case), which causes more noise in the main lobe and a greater number of errors of the second genus in the case of the use of generalized binary Barker sequences. With this, the compared systems of sequences are characterized by almost the same total bandwidth, and the fact that generalized binary Barker sequences also provide a lower pulse width in the main lobe after signal processing (by 1.5 times), which provides a greater maximum data transfer rate and spectral efficiency on the physical layer of spread-spectrum telecommunication system (up to 1.5 times). The research results were implemented in the production and research activities of the UkSATSE Flight Calibration & Rescue Service (Ukrainian State Air Traffic Services Enterprise «UkSATSE») and educational processes at the Faculty of Air Navigation, Electronics and Telecommunications (National Aviation University, Kyiv)

The detection of unknown waveforms in ESM receivers: FFT-based real-time solutions

Radars and airborne electronic support measures (ESMs) systems are locked in a tactical battle to detect each other whilst remaining undetected. Traditionally, the ESM system has a range advantage. Low probability of intercept (LPI) waveform designers are, however, more heavily exploiting the matched filter radar advantage and hence degrading the range advantage. There have been literature and internal, SELEX Galileo proposals to regain some ESM processing gain of low probability of intercept (LPI) waveforms. This study, however, has sought digital signal processing (DSP) solutions which are: (1) computationally simple; (2) backward-compatible with existing SELEX Galileo digital receivers (DRxs) and (3) have low resource requirements. The two contributions are complementary and result in a detector which is suitable for detection of most radar waveforms. The first contribution is the application of spatially variant apodization (SVA) in a detection role. Compared to conventional window functions, SVA was found to be beneficial for the detection of sinusoidal radar waveforms as it surpassed the fixed window function detectors in all scenarios tested. The second contribution shows by simulation that simple spectral smoothing techniques improved DRx LPI detection capability to a level similar to more complicated non-parametric spectral estimators and far in excess of the conventional (modified) periodogram. The DSP algorithms were implemented using model-based design (MBD). The implication is that a detector with improved conventional and LPI waveform detection capability can be created from the intellectual property (IP). Estimates of the improvement in SELEX Galileo DRx system detection range are provided in the conclusion